A North Korea envoy sent to Kuala Lumpur has disputed Malaysia's verdict on Mr Kim's cause of death.

Speaking to reporters outside the embassy, Ri Tong Il questioned the alleged use of VX, saying samples should be sent to the Organisation for the Prohibition of Chemical Weapons (OPCW).

"If it is true that it was used, then the samples should be sent to the office of OPCW," said Mr Ri, a former North Korean deputy ambassador to the UN.

Image:North Korea says Kim Jong-Un had a history of heart disease

"In case it is proved by the two separate international laboratories, with the same conclusion, then they should come to identify who is the one that made it. Who is the one that brought it into Malaysia."

He said the victim had a history of heart disease, and appeared to have been taking medicines for high blood pressure and diabetes.

"Therefore this is a strong indication the cause of the death is the heart attack," he said.

Malaysia also arrested a North Korean man, Ri Jong Chol, but now says it will deport him on Friday because there is not enough evidence to charge him.

South Korean intelligence officials say the murder was an assassination organised by North Korea because the victim was perceived at one point to be a threat to Kim Jong-Un's grip on power.